1. Field of the Invention
The present invention relates to a pressure gauge and more particularly, to an improved pressure gauge having two major functions, one of which is to show the present pressure of a piping system and the other of which is to show a preset pressure.
2. Brief Description of the Prior Art
In a piping system, such as in a hydraulic system, there needs a lot of gauges disposed to desired positions of the piping system and some sections of the system may be designed to allow only a certain pressure, i.e. the certain pressure must lower a preset standard pressure which should be shown such that operators can check the pressure all the time for the sake of safety. A conventional way to show the current pressure and the standard pressure in a piping system is shown in FIG. 1 wherein a first gauge 1 is used to show a preset standard pressure and a second gauge 6 is used to show the current pressure in the position where the second gauge 6 is disposed. However, such a way has the inherent shortcomings:
(1). The assembler must prepare at least two gauges, the first gauge and the second gauge, then the current pressure and the preset standard pressure are shown.
(2). It takes time to operate the first gauge and the second gauge separately.
(3). The current pressure is shown in the second gauge and the preset standard pressure is shown in the first gauge such that one must compare the two datum through calculation.
(4). It is experienced that such an arrangement has an inaccuracy up to 15%.
The present invention intends to provide an improved pressure gauge which has two sets of indicating needles, one of which shows the preset standard pressure and the other of which shows the current pressure so as to mitigate and/or obviate the above-mentioned problems.